29 research outputs found

    New procedures to estimate soil erodibility properties from a hole erosion test record

    Get PDF
    The estimation of representative values of the properties quantifying soil erodibility (critical shear stress and coefficient of soil erosion) is of great difficulty. The difficulty lies in the complexity of the phenomenon in question in addition to the uncertainty of the used experimentation (hole erosion test). In this paper, the procedure used to estimate these properties is presented, and two new procedures are proposed. The proposed procedures are more accurate for the quantification as well as to detect the initiation of the internal erosion. It is found that the erodibility properties depend on the hydraulic charge and that for one soil sample, it is possible to find more than one pair of solutions (critical shear stress, coefficient of soil erosion) which explains the non-observation of significant relationship between these two properties and other soil properties

    Studies of Electroconductive Magnetorheological Elastomers

    Get PDF
    Electroconductive magnetorheological elastomers (MREs) have attracted a wide scientific attention in recent years due to their potential applications as electric current elements, in seismic protection, in production of rehabilitation devices, and sensors or transducers of magnetic fields/mechanical tensions. A particular interest concerns their behavior under the influence of external magnetic and electric fields, since various physical properties (e.g., rheological, elastic, electrical) can be continuously and/or reversibly modified. In this chapter, we describe fabrication methods and structural properties from small-angle neutron scattering (SANS) of various isotropic and anisotropic MRE and hybrid MRE. We present and discuss the physical mechanisms leading to the main features of interest for various medical and technical applications, such as electrical (complex dielectric permittivity, electrical conductivity) and rheological (viscosity) properties

    Accurate detection of SARS-CoV-2 might be a challenge in the molecular biology laboratory for RT-PCR final results

    Get PDF
    The challenges we experience professionally always teach us to retreat, to document ourselves, to learn, to become better and to succeed in asserting ourselves in the fields we have trained and perfected throughout several years. This also happened in the pandemic times with Covid19, when we had to document RT-PCR techniques in order to be able to detect at the molecular level the SARS-CoV-2 virus responsible for disturbing the world worldwide. Thus, in the molecular biology laboratory, analysts must make very important decisions about the final result of the RT-PCR test to determine – given several analytical criteria – whether the result is negative, positive or equivocal. There are situations where the RT-PCR equipment does not detect all the genes responsible for a clearly positive result, or when the cycle threshold (Ct) is higher than specified in the reagent insert kit, and then it is the analyst's duty to decide what is the final result of molecular test. This paper brings to the fore the involvement, duty and the art of researchers and specialists who must assume the final result of the RT-PCR test in the detection of the SARS-CoV-2 virus responsible for the global pandemic of Covid-19

    Composite Materials Based on Polymeric Fibers Doped with Magnetic Nanoparticles: Synthesis, Properties and Applications

    No full text
    The increasingly sophisticated requirements of contemporary society, in relation to the assessment of environmental and health factors, are receiving much attention from the scientific community [...

    Magnetorheological Hybrid Elastomers Based on Silicone Rubber and Magnetorheological Suspensions with Graphene Nanoparticles: Effects of the Magnetic Field on the Relative Dielectric Permittivity and Electric Conductivity

    No full text
    Hybrid magnetorheological elastomers (hMREs) were manufactured based on silicone rubber, silicone oil, carbonyl iron microparticles, graphene nanoparticles and cotton fabric. Using the hMREs, flat capacitors (FCs) were made. Using the installation described in this paper, the electrical capacitance and the coefficient of dielectric losses of the hMREs were measured as a function of the intensity of the magnetic field superimposed over an alternating electric field. From the data obtained, the electrical conductivity, the relative dielectric permittivity and magnetodielectric effects are determined. It is observed that the obtained quantities are significantly influenced by the intensity of the magnetic field and the amount of graphene used

    Contaminated sites investigation. Objectives and methods

    No full text
    The past human activities, mainly that related to industrial development caused in many cases a strong contamination of soil, subsoil environment and of groundwater. This type of pollution is a concern because it poses risks to human health and to the ecosystem. More than this, such areas may not be used for new development, requiring solutions for remediation. The management of these sites consists of three main activities: characterization, remediation and, finally, redevelopment. The paper presents a case study dedicated to the first step of contaminated sites management, respectively characterization. This phase is very important, a good characterization could ensure a performant solution for the second step – remediation. Two new techniques for site characterization are presented, as technical principles, but also as performances obtained for the mentioned case study

    Magneto-Dielectric Effects in Polyurethane Sponge Modified with Carbonyl Iron for Applications in Low-Cost Magnetic Sensors

    No full text
    In this study, magnetizable polyurethane sponges (MSs) were obtained from commercial absorbent polyurethane sponges (PSs) doped with carbonyl iron microparticles (CIPs). Based on MSs, we manufactured cylindrical capacitors (CCs). The CCs were subjected to both a magnetic field and an alternating electric field, with a frequency of f=1 kHz. Using an RLC bridge, we measured the series electric capacitance, Cs, and the tangent of the loss angle, Ds. From the functions Cs=Cs(δ)CCs and Ds=Ds(δ)CCs, we extracted the components of the complex dielectric permittivity. It was found that the CIPs embedded in the MS matrix aggregated, leading to magneto-dielectric effects such as the enhancement of the complex dielectric permittivity components when applying the magnetic field as a principal effect and the enhancement of the electric capacitance and time constant of the capacitors as a secondary effect. The obtained results represent landmarks in the realization of low-cost magnetic field sensors, deformation and mechanical stress transducers in the robotics industry, etc

    Magnetizable Membranes Based on Cotton Microfibers, Honey, Carbonyl Iron, and Silver Nanoparticles: Effects of Static Magnetic Fields and Medium-Frequency Electric Fields on Electrical Properties

    No full text
    In this work, we present the manufacturing process of magnetizable membranes based on cotton microfibers, honey, carbonyl iron, and three different concentrations of silver microparticles. Each membrane is used as a dielectric material for the fabrication of electrical devices. By using the plane capacitor method, the electrical capacitance and dielectric loss tangent are measured in a medium-frequency alternating field superimposed on a static magnetic field. From the obtained data, the time constants of the devices, the components of complex dielectric permittivity, and the electrical conductivity of the membranes as a function of the electric field frequency and magnetic flux density can be extracted. The results show that the obtained membranes can be useful for the fabrication of low-cost and environmentally friendly magneto-active membranes that are required for various technical and biomedical applications

    Hybrid Magnetorheological Composites for Electric and Magnetic Field Sensors and Transducers

    No full text
    We present a simple, low-cost, and environmental-friendly method for the fabrication of hybrid magnetorheological composites (hMCs) based on cotton fibers soaked with a mixture of silicone oil (SO), carbonyl iron (CI) microparticles, and iron oxide microfibers (μF). The obtained hMCs, with various ratios (Φ) of SO and μF, are used as dielectric materials for manufacturing electrical devices. The equivalent electrical capacitance and resistance are investigated in the presence of an external magnetic field, with flux density B. Based on the recorded data, we obtain the variation of the relative dielectric constant (ϵr′), and electrical conductivity (σ), with Φ, and B. We show that, by increasing Φ, the distance between CI magnetic dipoles increases, and this leads to significant changes in the behaviour of ϵr′ and σ in a magnetic field. The results are explained by developing a theoretical model that is based on the dipolar approximation. They indicate that the obtained hMCs can be used in the fabrication of magneto-active fibers for fabrication of electric/magnetic field sensors and transducers

    Methodology and calculation model for recycling of composite construction products

    Get PDF
    The circular economy development has increased awareness on how construction products are treated at the end-of-life stage (EoL). With a growing recognition of the finite nature of primary resources, manufacturing processes are being shifted from the traditional take-make-dispose approach to a greater holistic practice, where valuable and/or scarce substances are recovered at the end of a product’s life. Life Cycle Assessment (LCA) is gaining wider attractiveness, as assessment of environmental impacts constitutes an effective quantitative decision tool to identifying sustainable solutions. At the same time, existing guidelines, technical specifications and methods for LCA assessment at EoL are rather heterogeneous regarding modelling and calculation of related secondary material and energy streams. For construction products, category rules for Environmental Product Declarations (EPD) according to EN 15804 (issued through the European Committee for Standardization) and the Product Environmental Footprint (PEF) (developed by the European Commission) currently represent the most advanced methodological references. The study presents the methodological approach per EN 15804, describing the benefits and loads beyond the typical disposal stage. Thus, the environmental impacts of a construction element can be credited in accord to its material and energetic recycling potential. An applied model is realized for water pipes made of composite material. The calculation is exemplified and comparative results of allocation scenarios per EN 15804 and PEF are discussed, demonstrating correlations between the normative requirements and their application. The results support further identification, assessment and ranking of recycling alternatives (i.e. mechanical, thermal, chemical)
    corecore